This invention relates to a method and apparatus for thermally oxidizing a gaseous material, e.g., a gas and/or vapor, in particular a gaseous material including volatile organic compounds or components. In particular, this invention relates to a method and apparatus for thermally oxidizing such gaseous material to render the gaseous material more environmentally acceptable and, preferably, to usefully transfer the heat evolved in such thermal oxidation, e.g. to thereby generate steam and/or hot water and/or hot oil.
Environmental concerns are becoming increasingly important, particularly in industries which produce, e.g., as primary products and/or by-products, volatile organic compounds or components, hereinafter referred to as VOC, which are released to the environment. Regulatory authorities have required that such VOC, in particular VOC which are hazardous to the health and/or safety of humans and/or other organisms, be treated to become and/or provide products which are more environmentally acceptable than the original VOC.
One useful approach to this pollution problem involves thermally oxidizing the VOC to produce materials which can be readily and safely released to the atmosphere. During the thermal oxidation of such VOC, a substantial amount of heat is produced. In certain instances where VOC is thermally oxidized, the resulting flue gases have been passed through a waste heat boiler installation to produce or generate steam and/or hot water. One problem which has arisen in the past is the process control of such a VOC thermal oxidation/waste heat boiler installation facility. This problem is particularly acute since the production of VOC to be thermally oxidized and the amount of steam/hot water required from the facility can be independent of each other.
Previous control systems have controlled the amount of added fuel, e.g., natural gas, propane, diesel fuel and the like, fed to the thermal oxidizer and the amount of air fed to the thermal oxidizer solely to regulate VOC emissions from the process. When steam demand is low, the fuel and air fed to the thermal oxidizer is maintained at a relatively high level so as to insure VOC thermal oxidation. Such control systems result in a substantial amount of energy being wasted by exhausting hot flue gases to the atmosphere. Moreover, previous systems utilized to destroy gaseous materials utilized very severe conditions which often involved unneeded combustion, which combustion itself often resulted in unnecessary air pollution.
In certain solid waste incinerators, the temperature in the combustion chamber is used to control the amount of fuel fed to the incinerator. See Zalman U.S. Pat. Nos. 3,530,807 and 548,761. However, in neither of these systems is gaseous material fed to a thermal oxidizer for thermal oxidation. Separate steam generators are employed in these systems. In addition, no steam is produced outside the combustion chamber itself, or for use elsewhere than in the incinerator to scrub particulates from the exhaust gas.
It would be clearly advantageous to provide a system which is controlled to provide effective and efficient thermal oxidation and useful heat transfer with controlled, e.g., reduced, fuel consumption.